Regarding Assaults, it's generally desirable if they can move faster than the Dire Wolf while still able to dish a lot of hurt. It's still about guns but this is perfectly understandable because Assaults are required to be able to, well, assault the enemy a.k.a. wrecking faces.
Speed (and agility) is only critical on Lights it appears. Just look at how people instantly scrutinize the running speed when a new Light is announced. They are also "asked" to be able to carry at least 4E and/or 2-3M at minimum when possible.
It's somewhat unclear on Mediums because perhaps surprisingly, I got the impression that people are still not sure about their role right until now. The Stormcrow is an amazing 'Mech for its weight and class and I guess it would be very difficult for others to match its level of performance.
So tell us how fast/agile you want your 'Mechs to move! Do you have a particular set of standards?
One thing I forgot to mention that this of course depends on the loadout a particular 'Mech carries, like (IMO) Adder's 97 kph untweaked speed is perfectly sufficient for her role as fire support, which generally means that she stays with the group and lends her firepower by shooting the enemies from a distance to keep them at bay.
Edited by Hit the Deck, 28 June 2015 - 03:09 AM.